Levels of Prostaglandin E Metabolite and Leukotriene E4 Are Increased in the Urine of Smokers: Evidence that Celecoxib Shunts Arachidonic Acid into the 5-Lipoxygenase Pathway

Cyclooxygenase-2 (COX-2) and 5-lipoxygenase (5-LO) play a role in inflammation and carcinogenesis. Biomarkers that reflect tobacco smoke-induced tissue injury are needed. In this study, levels of urinary prostaglandin E metabolite (PGE-M) and leukotriene E-4 (LTE4), biomarkers of the COX and 5-LO pathways, were compared in never smokers, former smokers, and current smokers. The effects of celecoxib, a selective COX-2 inhibitor, on levels of PGE-M and LTE4 were determined. Baseline levels of PGE-M and LTE4 were positively associated with smoking status; levels of PGE-M and LTE4 were higher in current versus never smokers. Treatment with 200 mg celecoxib twice daily for 6 +/- 1 days led to a reduction in urinary PGE- M levels in all groups but exhibited the greatest effect among subjects with high baseline PGE- M levels. Thus, high baseline PGE-M levels in smokers reflected increased COX-2 activity. In individuals with high baseline PGE-M levels, treatment with celecoxib led to a significant increase in levels of urinary LTE4, an effect that was not found in individuals with low baseline PGE- M levels. In conclusion, increased levels of urinary PGE- M and LTE4 were found in human smokers, a result that may reflect subclinical lung inflammation. In individuals with high baseline levels of PGE- M (elevated COX-2 activity), celecoxib administration shunted arachidonic acid into the proinflammatory 5-LO pathway. Because 5-LO activity and LTE4 have been suggested to play a role in cardiovascular disease, these results may help to explain the link between use of COX-2 inhibitors and cardiovascular complications.